This application claims priority of Taiwan Application No. 92201413, filed on Jan. 24, 2003.
1. Field of the Invention
The invention relates to a wood planing machine, more particularly to a wood planing machine with a height display unit for a cutter carriage.
2. Description of the Related Art
Referring to FIG. 1, a conventional wood planing machine is shown to include a machine body 10, left and right pairs of hollow posts 122, left and right pairs of screw rods 121, a cutter carriage 13, and a height display unit 15.
As illustrated, the machine body 10 has a base 11. The left and right pairs of screw rods 121 are mounted rotatably on the base 11 of the machine body 10. The hollow posts 122 are sleeved around the screw rods 121. The cutter carriage 13 is disposed above the base 11, and is mounted on the left and right pairs of hollow posts 122. The cutter carriage 13 threadedly engages left and right pairs of screw rods 123 (not visible) in such a manner that rotation of the screw rods 123 results in movement of the cutter carriage 13 along the hollow posts 122. The height display unit 15 includes a measuring scale mounted vertically on one of the hollow posts 122. A turning wheel 14 is fixed to the top end of one of the screw rods 121 to facilitate turning of the screw rods 121.
The aforesaid conventional wood planing machine is disadvantageous in that it is tiresome and inconvenient to read the scale of the height display unit 15 during the planing operation. In addition, human error in reading the scale of the height display unit 15 is likely to occur.
Therefore, the object of this invention is to provide a wood planing machine with a height display unit, which can overcome the aforementioned disadvantages of the prior art.
Accordingly, a wood planing machine of the present invention includes: a machine body having a base; a plurality of spaced apart screw rods extending uprightly in a longitudinal direction from and mounted rotatably on the base; a cutter carriage mounted movably on the screw rods so that rotation of the screw rods results in movement of the cutter carriage in the longitudinal direction; a detecting unit mounted on the machine body and including a light transmitter and a light receiver that cooperates with the light transmitter to define a gap therebetween and that generates an electrical signal upon receiving light from the light transmitter; an optical encoder wheel fixed to one of the screw rods so as to be co-rotatable therewith, having a peripheral end, and formed with a plurality of angularly spaced apart holes in the peripheral end, the peripheral end of the optical encoder wheel extending into the gap in such a manner that light emitted from the light transmitter is received by the light receiver only through the holes; and a control unit mounted on the machine body and electrically connected to the detecting unit for receiving the electrical signal from the light receiver and for calculating the number of revolutions of said one of the screw rods and the height of the cutter carriage relative to the base during rotation of the screw rods.